<!DOCTYPE html><html lang="zh-CN" data-theme="light"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width,initial-scale=1"><title>Thread类重要方法 | Reality</title><meta name="keywords" content="线程核心"><meta name="author" content="dtyy"><meta name="copyright" content="dtyy"><meta name="format-detection" content="telephone=no"><meta name="theme-color" content="#ffffff"><meta name="description" content="sleep方法sleep特性线程休眠 public static native void sleep(long millis) throws InterruptedException;  sleep特性  线程进入TIME_WAITING状态，不占用CPU资源，但不释放锁，包括synchronized和lock，到了指定时间继续执行。 自动响应中断，抛出InterruptedException异常">
<meta property="og:type" content="article">
<meta property="og:title" content="Thread类重要方法">
<meta property="og:url" content="https://dtyytop.gitee.io/2020/04/15/devnotes/zhi-mian-java/bing-fa/bing-fa-he-xin/1.6-thread-lei-de-chong-yao-fang-fa/index.html">
<meta property="og:site_name" content="Reality">
<meta property="og:description" content="sleep方法sleep特性线程休眠 public static native void sleep(long millis) throws InterruptedException;  sleep特性  线程进入TIME_WAITING状态，不占用CPU资源，但不释放锁，包括synchronized和lock，到了指定时间继续执行。 自动响应中断，抛出InterruptedException异常">
<meta property="og:locale" content="zh_CN">
<meta property="og:image" content="https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222634.jpg">
<meta property="article:published_time" content="2020-04-15T15:28:04.000Z">
<meta property="article:modified_time" content="2021-05-25T23:46:48.155Z">
<meta property="article:author" content="dtyy">
<meta property="article:tag" content="线程核心">
<meta name="twitter:card" content="summary">
<meta name="twitter:image" content="https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222634.jpg"><link rel="shortcut icon" href="/img/favicon.png"><link rel="canonical" href="https://dtyytop.gitee.io/2020/04/15/devnotes/zhi-mian-java/bing-fa/bing-fa-he-xin/1.6-thread-lei-de-chong-yao-fang-fa/"><link rel="preconnect" href="//cdn.jsdelivr.net"/><link rel="preconnect" href="//busuanzi.ibruce.info"/><meta/><link rel="stylesheet" href="/css/index.css"><link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@fortawesome/fontawesome-free/css/all.min.css" media="print" onload="this.media='all'"><script>const GLOBAL_CONFIG = { 
  root: '/',
  algolia: undefined,
  localSearch: {"path":"search.xml","languages":{"hits_empty":"找不到您查询的内容：${query}"}},
  translate: undefined,
  noticeOutdate: undefined,
  highlight: {"plugin":"prismjs","highlightCopy":true,"highlightLang":true,"highlightHeightLimit":false},
  copy: {
    success: '复制成功',
    error: '复制错误',
    noSupport: '浏览器不支持'
  },
  relativeDate: {
    homepage: false,
    post: true
  },
  runtime: '',
  date_suffix: {
    just: '刚刚',
    min: '分钟前',
    hour: '小时前',
    day: '天前',
    month: '个月前'
  },
  copyright: {"limitCount":50,"languages":{"author":"作者: dtyy","link":"链接: ","source":"来源: Reality","info":"著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。"}},
  lightbox: 'fancybox',
  Snackbar: undefined,
  source: {
    jQuery: 'https://cdn.jsdelivr.net/npm/jquery@latest/dist/jquery.min.js',
    justifiedGallery: {
      js: 'https://cdn.jsdelivr.net/npm/justifiedGallery/dist/js/jquery.justifiedGallery.min.js',
      css: 'https://cdn.jsdelivr.net/npm/justifiedGallery/dist/css/justifiedGallery.min.css'
    },
    fancybox: {
      js: 'https://cdn.jsdelivr.net/npm/@fancyapps/fancybox@latest/dist/jquery.fancybox.min.js',
      css: 'https://cdn.jsdelivr.net/npm/@fancyapps/fancybox@latest/dist/jquery.fancybox.min.css'
    }
  },
  isPhotoFigcaption: false,
  islazyload: false,
  isanchor: false
}</script><script id="config-diff">var GLOBAL_CONFIG_SITE = {
  title: 'Thread类重要方法',
  isPost: true,
  isHome: false,
  isHighlightShrink: false,
  isToc: true,
  postUpdate: '2021-05-26 07:46:48'
}</script><noscript><style type="text/css">
  #nav {
    opacity: 1
  }
  .justified-gallery img {
    opacity: 1
  }

  #recent-posts time,
  #post-meta time {
    display: inline !important
  }
</style></noscript><script>(win=>{
    win.saveToLocal = {
      set: function setWithExpiry(key, value, ttl) {
        if (ttl === 0) return
        const now = new Date()
        const expiryDay = ttl * 86400000
        const item = {
          value: value,
          expiry: now.getTime() + expiryDay,
        }
        localStorage.setItem(key, JSON.stringify(item))
      },

      get: function getWithExpiry(key) {
        const itemStr = localStorage.getItem(key)

        if (!itemStr) {
          return undefined
        }
        const item = JSON.parse(itemStr)
        const now = new Date()

        if (now.getTime() > item.expiry) {
          localStorage.removeItem(key)
          return undefined
        }
        return item.value
      }
    }
  
    win.getScript = url => new Promise((resolve, reject) => {
      const script = document.createElement('script')
      script.src = url
      script.async = true
      script.onerror = reject
      script.onload = script.onreadystatechange = function() {
        const loadState = this.readyState
        if (loadState && loadState !== 'loaded' && loadState !== 'complete') return
        script.onload = script.onreadystatechange = null
        resolve()
      }
      document.head.appendChild(script)
    })
  
      win.activateDarkMode = function () {
        document.documentElement.setAttribute('data-theme', 'dark')
        if (document.querySelector('meta[name="theme-color"]') !== null) {
          document.querySelector('meta[name="theme-color"]').setAttribute('content', '#0d0d0d')
        }
      }
      win.activateLightMode = function () {
        document.documentElement.setAttribute('data-theme', 'light')
        if (document.querySelector('meta[name="theme-color"]') !== null) {
          document.querySelector('meta[name="theme-color"]').setAttribute('content', '#ffffff')
        }
      }
      const t = saveToLocal.get('theme')
    
          if (t === 'dark') activateDarkMode()
          else if (t === 'light') activateLightMode()
        
      const asideStatus = saveToLocal.get('aside-status')
      if (asideStatus !== undefined) {
        if (asideStatus === 'hide') {
          document.documentElement.classList.add('hide-aside')
        } else {
          document.documentElement.classList.remove('hide-aside')
        }
      }
    
    const fontSizeVal = saveToLocal.get('global-font-size')
    if (fontSizeVal !== undefined) {
      document.documentElement.style.setProperty('--global-font-size', fontSizeVal + 'px')
    }
    })(window)</script><meta name="generator" content="Hexo 5.4.0"><link rel="alternate" href="/atom.xml" title="Reality" type="application/atom+xml">

<style>.github-emoji { position: relative; display: inline-block; width: 1.2em; min-height: 1.2em; overflow: hidden; vertical-align: top; color: transparent; }  .github-emoji > span { position: relative; z-index: 10; }  .github-emoji img, .github-emoji .fancybox { margin: 0 !important; padding: 0 !important; border: none !important; outline: none !important; text-decoration: none !important; user-select: none !important; cursor: auto !important; }  .github-emoji img { height: 1.2em !important; width: 1.2em !important; position: absolute !important; left: 50% !important; top: 50% !important; transform: translate(-50%, -50%) !important; user-select: none !important; cursor: auto !important; } .github-emoji-fallback { color: inherit; } .github-emoji-fallback img { opacity: 0 !important; }</style>
</head><body><div id="loading-box"><div class="loading-left-bg"></div><div class="loading-right-bg"></div><div class="spinner-box"><div class="configure-border-1"><div class="configure-core"></div></div><div class="configure-border-2"><div class="configure-core"></div></div><div class="loading-word">加载中...</div></div></div><div id="sidebar"><div id="menu-mask"></div><div id="sidebar-menus"><div class="author-avatar"><img class="avatar-img" src="https://i.loli.net/2021/02/24/5O1day2nriDzjSu.png" onerror="onerror=null;src='/img/friend_404.gif'" alt="avatar"/></div><div class="site-data"><div class="data-item is-center"><div class="data-item-link"><a href="/archives/"><div class="headline">文章</div><div class="length-num">95</div></a></div></div><div class="data-item is-center"><div class="data-item-link"><a href="/tags/"><div class="headline">标签</div><div class="length-num">28</div></a></div></div><div class="data-item is-center"><div class="data-item-link"><a href="/categories/"><div class="headline">分类</div><div class="length-num">16</div></a></div></div></div><hr/><div class="menus_items"><div class="menus_item"><a class="site-page" href="/"><i class="fa-fw fas fa-home"></i><span> 首页</span></a></div><div class="menus_item"><a class="site-page" href="/archives/"><i class="fa-fw fas fa-archive"></i><span> 归档</span></a></div><div class="menus_item"><a class="site-page" href="/tags/"><i class="fa-fw fas fa-tags"></i><span> 标签</span></a></div><div class="menus_item"><a class="site-page" href="/categories/"><i class="fa-fw fas fa-folder-open"></i><span> 分类</span></a></div><div class="menus_item"><a class="site-page" href="javascript:void(0);"><i class="fa-fw fas fa-list"></i><span> 清单</span><i class="fas fa-chevron-down expand"></i></a><ul class="menus_item_child"><li><a class="site-page child" href="/music/"><i class="fa-fw fas fa-music"></i><span> 音乐</span></a></li><li><a class="site-page child" href="/gallery/"><i class="fa-fw fas fa-images"></i><span> 图片</span></a></li><li><a class="site-page child" href="/movies/"><i class="fa-fw fas fa-video"></i><span> 电影</span></a></li></ul></div><div class="menus_item"><a class="site-page" href="/link/"><i class="fa-fw fas fa-link"></i><span> 友链</span></a></div><div class="menus_item"><a class="site-page" href="/about/"><i class="fa-fw fas fa-heart"></i><span> 关于</span></a></div></div></div></div><div class="post" id="body-wrap"><header class="post-bg" id="page-header" style="background-image: url('https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222634.jpg')"><nav id="nav"><span id="blog_name"><a id="site-name" href="/">Reality</a></span><div id="menus"><div id="search-button"><a class="site-page social-icon search"><i class="fas fa-search fa-fw"></i><span> 搜索</span></a></div><div class="menus_items"><div class="menus_item"><a class="site-page" href="/"><i class="fa-fw fas fa-home"></i><span> 首页</span></a></div><div class="menus_item"><a class="site-page" href="/archives/"><i class="fa-fw fas fa-archive"></i><span> 归档</span></a></div><div class="menus_item"><a class="site-page" href="/tags/"><i class="fa-fw fas fa-tags"></i><span> 标签</span></a></div><div class="menus_item"><a class="site-page" href="/categories/"><i class="fa-fw fas fa-folder-open"></i><span> 分类</span></a></div><div class="menus_item"><a class="site-page" href="javascript:void(0);"><i class="fa-fw fas fa-list"></i><span> 清单</span><i class="fas fa-chevron-down expand"></i></a><ul class="menus_item_child"><li><a class="site-page child" href="/music/"><i class="fa-fw fas fa-music"></i><span> 音乐</span></a></li><li><a class="site-page child" href="/gallery/"><i class="fa-fw fas fa-images"></i><span> 图片</span></a></li><li><a class="site-page child" href="/movies/"><i class="fa-fw fas fa-video"></i><span> 电影</span></a></li></ul></div><div class="menus_item"><a class="site-page" href="/link/"><i class="fa-fw fas fa-link"></i><span> 友链</span></a></div><div class="menus_item"><a class="site-page" href="/about/"><i class="fa-fw fas fa-heart"></i><span> 关于</span></a></div></div><div id="toggle-menu"><a class="site-page"><i class="fas fa-bars fa-fw"></i></a></div></div></nav><div id="post-info"><h1 class="post-title">Thread类重要方法</h1><div id="post-meta"><div class="meta-firstline"><span class="post-meta-date"><i class="far fa-calendar-alt fa-fw post-meta-icon"></i><span class="post-meta-label">发表于</span><time class="post-meta-date-created" datetime="2020-04-15T15:28:04.000Z" title="发表于 2020-04-15 23:28:04">2020-04-15</time><span class="post-meta-separator">|</span><i class="fas fa-history fa-fw post-meta-icon"></i><span class="post-meta-label">更新于</span><time class="post-meta-date-updated" datetime="2021-05-25T23:46:48.155Z" title="更新于 2021-05-26 07:46:48">2021-05-26</time></span><span class="post-meta-categories"><span class="post-meta-separator">|</span><i class="fas fa-inbox fa-fw post-meta-icon"></i><a class="post-meta-categories" href="/categories/%E5%B9%B6%E5%8F%91%E7%BC%96%E7%A8%8B/">并发编程</a><i class="fas fa-angle-right post-meta-separator"></i><i class="fas fa-inbox fa-fw post-meta-icon"></i><a class="post-meta-categories" href="/categories/%E5%B9%B6%E5%8F%91%E7%BC%96%E7%A8%8B/%E7%BA%BF%E7%A8%8B%E6%A0%B8%E5%BF%83/">线程核心</a></span></div><div class="meta-secondline"><span class="post-meta-separator">|</span><span class="post-meta-wordcount"><i class="far fa-file-word fa-fw post-meta-icon"></i><span class="post-meta-label">字数总计:</span><span class="word-count">938</span><span class="post-meta-separator">|</span><i class="far fa-clock fa-fw post-meta-icon"></i><span class="post-meta-label">阅读时长:</span><span>3分钟</span></span><span class="post-meta-separator">|</span><span class="post-meta-pv-cv" id="" data-flag-title="Thread类重要方法"><i class="far fa-eye fa-fw post-meta-icon"></i><span class="post-meta-label">阅读量:</span><span id="busuanzi_value_page_pv"></span></span></div></div></div></header><main class="layout" id="content-inner"><div id="post"><article class="post-content" id="article-container"><h2 id="sleep方法"><a href="#sleep方法" class="headerlink" title="sleep方法"></a>sleep方法</h2><h3 id="sleep特性"><a href="#sleep特性" class="headerlink" title="sleep特性"></a>sleep特性</h3><p>线程休眠</p>
<pre class="line-numbers language-java" data-language="java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">native</span> <span class="token keyword">void</span> <span class="token function">sleep</span><span class="token punctuation">(</span><span class="token keyword">long</span> millis<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">InterruptedException</span><span class="token punctuation">;</span><span aria-hidden="true" class="line-numbers-rows"><span></span></span></code></pre>

<p>sleep特性</p>
<ul>
<li>线程进入TIME_WAITING状态，不占用CPU资源，但不释放锁，包括synchronized和lock，到了指定时间继续执行。</li>
<li>自动响应中断，抛出InterruptedException异常，并清除中断状态。</li>
</ul>
<h3 id="优雅的休眠方式"><a href="#优雅的休眠方式" class="headerlink" title="优雅的休眠方式"></a>优雅的休眠方式</h3><pre class="line-numbers language-none"><code class="language-none">TimeUnit.HOURS.sleep(1);<span aria-hidden="true" class="line-numbers-rows"><span></span></span></code></pre>

<p>相对于Thread.sleep(num)来说，优势在于</p>
<ul>
<li>Thread.sleep(n)只接受ms单位，使用TimeUnit更加灵活，代码也更加清晰；</li>
<li>Thread.sleep(n)在时间参数小于0时会抛出IllegalArgumentException异常，而TimeUnit对时间做了预处理，不会抛出异常，避免中断程序。</li>
</ul>
<p><img src="https://gitee.com/dtyytop/blogimage/raw/master/img/20210517002304.png" alt="img"></p>
<p>第一点和第四点进行解释（见上一小节）。</p>
<h2 id="join方法"><a href="#join方法" class="headerlink" title="join方法"></a>join方法</h2><h3 id="join基本用法"><a href="#join基本用法" class="headerlink" title="join基本用法"></a>join基本用法</h3><p>阻塞调用join方法的线程，知道该线程执行结束。例如等待多个线程加载完资源。</p>
<pre class="line-numbers language-java" data-language="java"><code class="language-java">thread1<span class="token punctuation">.</span><span class="token function">start</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
thread2<span class="token punctuation">.</span><span class="token function">start</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
thread1<span class="token punctuation">.</span><span class="token function">join</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 可抛出中断异常</span>
thread2<span class="token punctuation">.</span><span class="token function">join</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"所有线程都运行结束"</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<ul>
<li>调用join方法后，调用线程的状态是WAITING。</li>
<li>中断执行join语句线程时，抛InterruptedException异常，清除中断标识。</li>
</ul>
<p>操作Java线程的大原则是不出错，优先使用Java现成的工具类。join方法在实际开发中使用较少，可以使用CountDownLatch或者CyclicBarrier类来代替。</p>
<h3 id="join源码分析"><a href="#join源码分析" class="headerlink" title="join源码分析"></a>join源码分析</h3><pre class="line-numbers language-java" data-language="java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">final</span> <span class="token keyword">synchronized</span> <span class="token keyword">void</span> <span class="token function">join</span><span class="token punctuation">(</span><span class="token keyword">long</span> millis<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">InterruptedException</span> <span class="token punctuation">{</span>
    <span class="token keyword">long</span> base <span class="token operator">=</span> <span class="token class-name">System</span><span class="token punctuation">.</span><span class="token function">currentTimeMillis</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">long</span> now <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
    <span class="token comment">// 参数校验</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>millis <span class="token operator">&lt;</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">throw</span> <span class="token keyword">new</span> <span class="token class-name">IllegalArgumentException</span><span class="token punctuation">(</span><span class="token string">"timeout value is negative"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    <span class="token comment">// 核心代码</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>millis <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token comment">// 无限等待直到调用线程结束</span>
        <span class="token keyword">while</span> <span class="token punctuation">(</span><span class="token function">isAlive</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token function">wait</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
        <span class="token comment">// 超时时间结束，便不再等待</span>
        <span class="token keyword">while</span> <span class="token punctuation">(</span><span class="token function">isAlive</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">long</span> delay <span class="token operator">=</span> millis <span class="token operator">-</span> now<span class="token punctuation">;</span>
            <span class="token keyword">if</span> <span class="token punctuation">(</span>delay <span class="token operator">&lt;=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
                <span class="token keyword">break</span><span class="token punctuation">;</span>
            <span class="token punctuation">}</span>
            <span class="token function">wait</span><span class="token punctuation">(</span>delay<span class="token punctuation">)</span><span class="token punctuation">;</span>
            now <span class="token operator">=</span> <span class="token class-name">System</span><span class="token punctuation">.</span><span class="token function">currentTimeMillis</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">-</span> base<span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<p>上面join(long)方法中，如果millis不为0，内部采用了wait(long)方法，超时自动唤醒。而millis为0时，只调用了wait(0)，没有唤醒的代码。</p>
<pre class="line-numbers language-none"><code class="language-none">while (isAlive()) {    wait(0); }<span aria-hidden="true" class="line-numbers-rows"><span></span></span></code></pre>

<p>注意这个wait()方法是Object类中的方法，再来看sychronized的是谁：</p>
<pre class="line-numbers language-none"><code class="language-none">public final synchronized void join(long millis) throws InterruptedException { ... }<span aria-hidden="true" class="line-numbers-rows"><span></span></span></code></pre>

<p>由于普通方法加synchronized，相当于synchronized(this)，this指的是当前类实例的引用，也就是说主线程拥有了某个thread对象的锁。</p>
<p>查看hotspot源码</p>
<pre class="line-numbers language-c++" data-language="c++"><code class="language-c++">// https://github.com/openjdk-mirror/jdk7u-hotspot/blob/master/src/share/vm/runtime/thread.cpp
void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
    ...
    ensure_join(this);
    ...
}

// 通知thread对象的等待线程
static void ensure_join(JavaThread* thread) {
  // We do not need to grap the Threads_lock, since we are operating on ourself.
  Handle threadObj(thread, thread-&gt;threadObj());
  assert(threadObj.not_null(), "java thread object must exist");
  ObjectLocker lock(threadObj, thread);
  // Ignore pending exception (ThreadDeath), since we are exiting anyway
  thread-&gt;clear_pending_exception();
  // Thread is exiting. So set thread_status field in  java.lang.Thread class to TERMINATED.
  java_lang_Thread::set_thread_status(threadObj(), java_lang_Thread::TERMINATED);
  // Clear the native thread instance - this makes isAlive return false and allows the join()
  // to complete once we've done the notify_all below
  java_lang_Thread::set_thread(threadObj(), NULL);
  // 唤醒thread对象上的线程
  lock.notify_all(thread);
  // Ignore pending exception (ThreadDeath), since we are exiting anyway
  thread-&gt;clear_pending_exception();
}<span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<p>当子线程thread执行完毕的时候，jvm会自动唤醒阻塞在thread对象上的线程。</p>
<p>小结：<u>join方法是synchronized方法，内部调用了wait方法。这个过程的目的是让持有锁的线程进入阻塞状态，而这个锁正是join方法的调用线程。</u>因此join方法可以等价为：</p>
<pre class="line-numbers language-java" data-language="java"><code class="language-java">thread<span class="token punctuation">.</span><span class="token function">join</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// 等价代码</span>
<span class="token keyword">synchronized</span> <span class="token punctuation">(</span>thread<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    subThread<span class="token punctuation">.</span><span class="token function">wait</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span aria-hidden="true" class="line-numbers-rows"><span></span><span></span><span></span><span></span><span></span></span></code></pre>

<p>至于唤醒，在thread线程结束时，JVM会调用lock.notify_all(thread)，唤醒thread这把锁上的线程。</p>
<h3 id="面试点：join方法后线程状态–WAITING"><a href="#面试点：join方法后线程状态–WAITING" class="headerlink" title="面试点：join方法后线程状态–WAITING"></a>面试点：join方法后线程状态–WAITING</h3><h2 id="yield方法"><a href="#yield方法" class="headerlink" title="yield方法"></a>yield方法</h2><p>释放掉当前的CPU时间片。释放后，线程是RUNNABLE状态，下一次线程调度仍然可能调度起来。JVM不保证遵循这一规则，例如资源充足情况下，调用yield方法，线程可能不释放时间片。实际开发中，不使用yield方法。</p>
<p>与sleep方法的区别是，是否可以随时被调度。yield是对调度器的提示，不一定执行，而sleep会执行。</p>
</article><div class="post-copyright"><div class="post-copyright__author"><span class="post-copyright-meta">文章作者: </span><span class="post-copyright-info"><a href="mailto:undefined">dtyy</a></span></div><div class="post-copyright__type"><span class="post-copyright-meta">文章链接: </span><span class="post-copyright-info"><a href="https://dtyytop.gitee.io/2020/04/15/devnotes/zhi-mian-java/bing-fa/bing-fa-he-xin/1.6-thread-lei-de-chong-yao-fang-fa/">https://dtyytop.gitee.io/2020/04/15/devnotes/zhi-mian-java/bing-fa/bing-fa-he-xin/1.6-thread-lei-de-chong-yao-fang-fa/</a></span></div><div class="post-copyright__notice"><span class="post-copyright-meta">版权声明: </span><span class="post-copyright-info">本博客所有文章除特别声明外，均采用 <a href="https://creativecommons.org/licenses/by-nc-sa/4.0/" target="_blank">CC BY-NC-SA 4.0</a> 许可协议。转载请注明来自 <a href="https://dtyytop.gitee.io" target="_blank">Reality</a>！</span></div></div><div class="tag_share"><div class="post-meta__tag-list"><a class="post-meta__tags" href="/tags/%E7%BA%BF%E7%A8%8B%E6%A0%B8%E5%BF%83/">线程核心</a></div><div class="post_share"><div class="social-share" data-image="https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222634.jpg" data-sites="facebook,twitter,wechat,weibo,qq"></div><link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/social-share.js/dist/css/share.min.css" media="print" onload="this.media='all'"><script src="https://cdn.jsdelivr.net/npm/social-share.js/dist/js/social-share.min.js" defer></script></div></div><div class="post-reward"><div class="reward-button button--animated"><i class="fas fa-qrcode"></i> 打赏</div><div class="reward-main"><ul class="reward-all"><li class="reward-item"><a href="https://gitee.com/dtyytop/blogimage/raw/master/img/20210515001034.png" target="_blank"><img class="post-qr-code-img" src="https://gitee.com/dtyytop/blogimage/raw/master/img/20210515001034.png" alt="wechat"/></a><div class="post-qr-code-desc">wechat</div></li><li class="reward-item"><a href="https://gitee.com/dtyytop/blogimage/raw/master/img/20210515001009.png" target="_blank"><img class="post-qr-code-img" src="https://gitee.com/dtyytop/blogimage/raw/master/img/20210515001009.png" alt="alipay"/></a><div class="post-qr-code-desc">alipay</div></li></ul></div></div><nav class="pagination-post" id="pagination"><div class="prev-post pull-left"><a href="/2020/04/15/devnotes/zhi-mian-java/bing-fa/bing-fa-he-xin/2.1-java-nei-cun-mo-xing-yu-san-da-te-xing/"><img class="prev-cover" src="https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222621.jpg" onerror="onerror=null;src='/img/404.jpg'" alt="cover of previous post"><div class="pagination-info"><div class="label">上一篇</div><div class="prev_info">Java内存模型</div></div></a></div><div class="next-post pull-right"><a href="/2020/04/15/devnotes/zhi-mian-java/bing-fa/bing-fa-he-xin/1.8-bing-fa-an-quan-de-xiang-guan-gai-nian/"><img class="next-cover" src="https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222615.jpg" onerror="onerror=null;src='/img/404.jpg'" alt="cover of next post"><div class="pagination-info"><div class="label">下一篇</div><div class="next_info">多线程带来的线程安全和性能问题</div></div></a></div></nav><div class="relatedPosts"><div class="headline"><i class="fas fa-thumbs-up fa-fw"></i><span> 相关推荐</span></div><div class="relatedPosts-list"><div><a href="/2020/04/15/devnotes/zhi-mian-java/bing-fa/bing-fa-he-xin/1.1-java-duo-xian-cheng-dao-di-you-ji-chong-shi-xian-fang-shi/" title="Java多线程到底有几种实现方式"><img class="cover" src="https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222629.jpg" alt="cover"><div class="content is-center"><div class="date"><i class="far fa-calendar-alt fa-fw"></i> 2020-04-15</div><div class="title">Java多线程到底有几种实现方式</div></div></a></div><div><a href="/2020/04/15/devnotes/zhi-mian-java/bing-fa/bing-fa-he-xin/1.2-xian-cheng-qi-dong/" title="线程启动原理"><img class="cover" src="https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222615.jpg" alt="cover"><div class="content is-center"><div class="date"><i class="far fa-calendar-alt fa-fw"></i> 2020-04-15</div><div class="title">线程启动原理</div></div></a></div></div></div></div><div class="aside-content" id="aside-content"><div class="card-widget card-info"><div class="card-info-avatar is-center"><img class="avatar-img" src="https://i.loli.net/2021/02/24/5O1day2nriDzjSu.png" onerror="this.onerror=null;this.src='/img/friend_404.gif'" alt="avatar"/><div class="author-info__name">dtyy</div><div class="author-info__description">Java全栈</div></div><div class="card-info-data"><div class="card-info-data-item is-center"><a href="/archives/"><div class="headline">文章</div><div class="length-num">95</div></a></div><div class="card-info-data-item is-center"><a href="/tags/"><div class="headline">标签</div><div class="length-num">28</div></a></div><div class="card-info-data-item is-center"><a href="/categories/"><div class="headline">分类</div><div class="length-num">16</div></a></div></div><a class="button--animated" id="card-info-btn" target="_blank" rel="noopener" href="https://gitee.com/dtyytop"><i class="fab fa-github"></i><span>Follow Me</span></a><div class="card-info-social-icons is-center"><a class="social-icon" href="https://gitee.com/dtyytop" target="_blank" title="Github"><i class="fab fa-github"></i></a><a class="social-icon" href="mailto:1607961042@qq.com" target="_blank" title="Email"><i class="fas fa-envelope"></i></a></div></div><div class="card-widget card-announcement"><div class="item-headline"><i class="fas fa-bullhorn card-announcement-animation"></i><span>公告</span></div><div class="announcement_content">This is my Blog</div></div><div class="sticky_layout"><div class="card-widget" id="card-toc"><div class="item-headline"><i class="fas fa-stream"></i><span>目录</span></div><div class="toc-content"><ol class="toc"><li class="toc-item toc-level-2"><a class="toc-link" href="#sleep%E6%96%B9%E6%B3%95"><span class="toc-number">1.</span> <span class="toc-text">sleep方法</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#sleep%E7%89%B9%E6%80%A7"><span class="toc-number">1.1.</span> <span class="toc-text">sleep特性</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E4%BC%98%E9%9B%85%E7%9A%84%E4%BC%91%E7%9C%A0%E6%96%B9%E5%BC%8F"><span class="toc-number">1.2.</span> <span class="toc-text">优雅的休眠方式</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#join%E6%96%B9%E6%B3%95"><span class="toc-number">2.</span> <span class="toc-text">join方法</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#join%E5%9F%BA%E6%9C%AC%E7%94%A8%E6%B3%95"><span class="toc-number">2.1.</span> <span class="toc-text">join基本用法</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#join%E6%BA%90%E7%A0%81%E5%88%86%E6%9E%90"><span class="toc-number">2.2.</span> <span class="toc-text">join源码分析</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E9%9D%A2%E8%AF%95%E7%82%B9%EF%BC%9Ajoin%E6%96%B9%E6%B3%95%E5%90%8E%E7%BA%BF%E7%A8%8B%E7%8A%B6%E6%80%81%E2%80%93WAITING"><span class="toc-number">2.3.</span> <span class="toc-text">面试点：join方法后线程状态–WAITING</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#yield%E6%96%B9%E6%B3%95"><span class="toc-number">3.</span> <span class="toc-text">yield方法</span></a></li></ol></div></div><div class="card-widget card-recent-post"><div class="item-headline"><i class="fas fa-history"></i><span>最新文章</span></div><div class="aside-list"><div class="aside-list-item"><a class="thumbnail" href="/2021/06/02/devnotes/ji-qun-yan-jin/nginx/1.3-nginx-jin-cheng-mo-xing-yu-shi-jian-chu-li-ji-zhi/" title="Nginx进程模型"><img src="https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222600.jpg" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="Nginx进程模型"/></a><div class="content"><a class="title" href="/2021/06/02/devnotes/ji-qun-yan-jin/nginx/1.3-nginx-jin-cheng-mo-xing-yu-shi-jian-chu-li-ji-zhi/" title="Nginx进程模型">Nginx进程模型</a><time datetime="2021-06-01T16:00:00.000Z" title="发表于 2021-06-02 00:00:00">2021-06-02</time></div></div><div class="aside-list-item"><a class="thumbnail" href="/2021/06/02/devnotes/ji-qun-yan-jin/nginx/1.4-nginx-he-xin-wen-jian-jie-gou-fen-xi/" title="Nginx核心配置结构"><img src="https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222629.jpg" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="Nginx核心配置结构"/></a><div class="content"><a class="title" href="/2021/06/02/devnotes/ji-qun-yan-jin/nginx/1.4-nginx-he-xin-wen-jian-jie-gou-fen-xi/" title="Nginx核心配置结构">Nginx核心配置结构</a><time datetime="2021-06-01T16:00:00.000Z" title="发表于 2021-06-02 00:00:00">2021-06-02</time></div></div><div class="aside-list-item"><a class="thumbnail" href="/2021/05/30/devnotes/ji-qun-yan-jin/nginx/1.2-wei-shi-me-xuan-ze-nginx/" title="集群、代理与Nginx"><img src="https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222629.jpg" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="集群、代理与Nginx"/></a><div class="content"><a class="title" href="/2021/05/30/devnotes/ji-qun-yan-jin/nginx/1.2-wei-shi-me-xuan-ze-nginx/" title="集群、代理与Nginx">集群、代理与Nginx</a><time datetime="2021-05-29T16:00:00.000Z" title="发表于 2021-05-30 00:00:00">2021-05-30</time></div></div><div class="aside-list-item"><a class="thumbnail" href="/2021/05/30/devnotes/ji-qun-yan-jin/redis/redis-zhu-cong-fu-zhi-yu-yuan-li/" title="Redis主从复制架构与原理"><img src="https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222646.jpg" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="Redis主从复制架构与原理"/></a><div class="content"><a class="title" href="/2021/05/30/devnotes/ji-qun-yan-jin/redis/redis-zhu-cong-fu-zhi-yu-yuan-li/" title="Redis主从复制架构与原理">Redis主从复制架构与原理</a><time datetime="2021-05-29T16:00:00.000Z" title="发表于 2021-05-30 00:00:00">2021-05-30</time></div></div><div class="aside-list-item"><a class="thumbnail" href="/2021/05/30/devnotes/ji-qun-yan-jin/redis/redis-chi-jiu-hua-ji-zhi/" title="Redis的两种持久化机制"><img src="https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222634.jpg" onerror="this.onerror=null;this.src='/img/404.jpg'" alt="Redis的两种持久化机制"/></a><div class="content"><a class="title" href="/2021/05/30/devnotes/ji-qun-yan-jin/redis/redis-chi-jiu-hua-ji-zhi/" title="Redis的两种持久化机制">Redis的两种持久化机制</a><time datetime="2021-05-29T16:00:00.000Z" title="发表于 2021-05-30 00:00:00">2021-05-30</time></div></div></div></div></div></div></main><footer id="footer" style="background-image: url('https://gitee.com/dtyytop/blogimage/raw/master/img/cover/20210525222634.jpg')"><div id="footer-wrap"><div class="copyright">&copy;2020 - 2021 By dtyy</div><div class="framework-info"><span>框架 </span><a target="_blank" rel="noopener" href="https://hexo.io">Hexo</a><span class="footer-separator">|</span><span>主题 </span><a target="_blank" rel="noopener" href="https://github.com/jerryc127/hexo-theme-butterfly">Butterfly</a></div></div></footer></div><div id="rightside"><div id="rightside-config-hide"><button id="readmode" type="button" title="阅读模式"><i class="fas fa-book-open"></i></button><button id="font-plus" type="button" title="放大字体"><i class="fas fa-plus"></i></button><button id="font-minus" type="button" title="缩小字体"><i class="fas fa-minus"></i></button><button id="darkmode" type="button" title="浅色和深色模式转换"><i class="fas fa-adjust"></i></button><button id="hide-aside-btn" type="button" title="单栏和双栏切换"><i class="fas fa-arrows-alt-h"></i></button></div><div id="rightside-config-show"><button id="rightside_config" type="button" title="设置"><i class="fas fa-cog fa-spin"></i></button><button class="close" id="mobile-toc-button" type="button" title="目录"><i class="fas fa-list-ul"></i></button><button id="go-up" type="button" title="回到顶部"><i class="fas fa-arrow-up"></i></button></div></div><div id="local-search"><div class="search-dialog"><div class="search-dialog__title" id="local-search-title">本地搜索</div><div id="local-input-panel"><div id="local-search-input"><div class="local-search-box"><input class="local-search-box--input" placeholder="搜索文章" type="text"/></div></div></div><hr/><div id="local-search-results"></div><span class="search-close-button"><i class="fas fa-times"></i></span></div><div id="search-mask"></div></div><div><script src="/js/utils.js"></script><script src="/js/main.js"></script><script src="https://cdn.jsdelivr.net/npm/instant.page/instantpage.min.js" type="module"></script><script src="/js/search/local-search.js"></script><script>var preloader = {
  endLoading: () => {
    document.body.style.overflow = 'auto';
    document.getElementById('loading-box').classList.add("loaded")
  },
  initLoading: () => {
    document.body.style.overflow = '';
    document.getElementById('loading-box').classList.remove("loaded")

  }
}
window.addEventListener('load',preloader.endLoading())</script><div class="js-pjax"></div><script defer="defer" id="ribbon" src="https://cdn.jsdelivr.net/npm/butterfly-extsrc@1/dist/canvas-ribbon.min.js" size="150" alpha="0.6" zIndex="-1" mobile="false" data-click="false"></script><script src="https://cdn.jsdelivr.net/npm/butterfly-extsrc@1/dist/activate-power-mode.min.js"></script><script>POWERMODE.colorful = true;
POWERMODE.shake = true;
POWERMODE.mobile = false;
document.body.addEventListener('input', POWERMODE);
</script><script async data-pjax src="//busuanzi.ibruce.info/busuanzi/2.3/busuanzi.pure.mini.js"></script></div></body></html>